Bolts? Studs?

[Blackdog]

Just wondering what the differance wld be between the ARP Head bolts and ARP Studs. Thanks

[*D-Joker*]

well they say that studs are stronger than bolts, they can be tensioned better (more you can torque down the head), and they way the studs are screwed in and threaded, they locked in better etc.

are you gonna b building up your motor or you gonna leave it real basic with minor tuning???

[oregonjoe]

Originally Posted by Blackdog

Just wondering what the differance wld be between the ARP Head bolts and ARP Studs. Thanks

About $40

I have debated this a long while in deciding which way to go on my rebuild. When I tore the engine apart, one of the head bolts was severely damaged from a coolant leak that made it unusable – so I had to purchase a head bolt set. After much looking around I could not find OEM head bolts but only found ARP bolts or studs. ARP bolts were about $100 and ARP Studs were $140.

Then I talked to my machine shop guy who builds racers and he explained that Head studs were used to mainly make assembly and disassembly easier since studs do not have to removed all the time when they would take heads off which was on a weekly basis and that wears on the block threads. So I thought OK, Bolts would be fine since I am only going to this every 20 years!

Then he explained the advantage of studs was that they could be set all the way down into the block threads in relaxed state thereby getting more bite into he block when torque down. Head bolts can’t reach as far down into the block and the toque down starts to stretch them before they can reach full clamping force. As a result, studs can achieve more pressure on the gasket and mating surface. As the block and aluminum heads expand at different rates, over time they grind on the gasket to wear it down. Increased clamping force will limit head movement and reduce gasket movement. I asked what about too much torque to break the block threads or crack the block. He said there is more then enough structure in the block to take the extra 10 pounds of torque down that studs can achieve.

So not only can the head withstand higher compression – the gasket mating will last much longer and more importantly will compensate for surface defects that appear over time. All engine parts are new only once – they only deteriorate from there

Overall, since studs can be installed into the block in a relaxed state and then put under tension – more clamping force can be achieved on the gasket then bolts. At $40 difference on a $1200 project – I decided to go with the studs. Got them from

www.horsepowerfreaks.com
ARP 203-4202 ARP (86-92) Supra MK3 Head Studs - 7MGTE (includes nuts) $134

Ordered on Wednesday via UPS Ground – arrived on Thursday.

The only drawback is installing the head with the studs in place. Haven’t done that yet but others have. I figured since I got the hood removed, can’t be too bad?

[mk3teen]

i was wondering cuz im curently tearing down my 7mgte to replace my head gasket cuz it finally gave out. im gunna replace it with a metal head gasket, thing is my dad who is financing most of this doesnt think we need to get arp head studs or even bolts, he thinks the bolts we take can be reused, everyone has told me u NEED arp headstuds wen replacing with mhg, how do i explain tht i really need thm?

[cre]

You don't NEED ARP bolts or studs... the OEM Toyota bolts are VERY strong and very durable... and they're reusable. No promises about off brand OEM replacements though. It is my personal preference to replace 20 year old fasteners though.

Unless you're doing a massive build I wouldn't worry about studs over bolts. Studs torque more evenly and there is less trouble with stiction while installing. Most people say you needn't worry about retorquing studs as you do with head bolts, but I strongly recommend it with any new fasteners.

[mk3teen]

yeah see i want new ones cuz a freind who never got around to rebuilding his motor is sellin me the greddy mhg and arp studs for 250 but my dad complained and wants to reuse the same studs but i dont think after 20 years thts a good idea.

[oregonjoe]

I found that when I removed the old Head bolts, they were damaged by the coolant fluid from the head gasket leak and could/would not reuse them. It alot of money and time to redo a head so the small extra expense to put new studs in is worth it in my opinion.

I used studs and really like how they torgued down to 90 lbs compared to 70 on stock.

Metal head gaskets can and should be torqued down more then stock. At $250 for the set I'd tell you dad its a deal and helps avoids paying more to redo the job again sooner then you might want.

Only thing about Metal Head gaskets is the amount of work to really, really, really clean up both the block deck and head surfaces as they will need to be perfect.

Studs run about $40 more then bolts ($140) but allow you torque down more. For a NA it is not such a big deal but for turbo ...

[cre]

Originally Posted by oregonjoe

Metal head gaskets can and should be torqued down more then stock.

Heh, the stock head gasket needs to be torqued down more than stock. Probably why everyone does.

[oregonjoe]

Totally agree if you mean that all head gaskets need to be torqued down more then stock torque which I believe was 55-60??? I do think that most rebuilds are going for 70 or more??

Anyway - my point was that studs make it easier to get even higher torque then factory bolts - and the more torque the better!

I have wondered if you can torque down a composite gasket too much? to a point that the crush rings expand too much into the coolant and oil passages? Don't think metal head gaskets have the same issue.

Only real way to tell is to put one in - torque to 90 then run for a few years and take apart??

[cre]

Stock is 58 ft lbs. The recommended torque for our size head bolts with aluminum heads is 72 or 75 ft lbs. Studs are torqued to about 90, IIRC. BOTH values vary depending on what lubricant is used for the install. I only remember some of the reasons for the differences so I'm not going to try to get in depth with this as I'd just be guessing at the end.

A retorque is good medicine for any new fasteners or gaskets (especially composite gaskets). You need to back off the fastener anywhere from one quarter of a turn to up to a full turn... you don't want to over do it though, just enough to free up the fastener. Then retorque to spec. If striction is encountered back the fastener off a little more than the first time and then torque again. When torquing ANY type of fastener you want the fastener to move smoothly and steadily the whole way... striction can cause big variances in torque readings. Also, when backing them off it isn't a bad idea to back them all off and then retorque uniformly.

As long as you properly tend to the threads in the block, lubricate with a high grade lubricant (not just one that claims to be good ) and retorque PROPERLY either type will contribute to a seal which may very well out live the car; Depends on how well everything else was tended to.

Studs do allow for a higher clamping force (accuracy is more to do with the installer IMO) and definitely gives you a better piece of mind (especially with certain types of head gasket construction).

Originally Posted by oregonjoe

I have wondered if you can torque down a composite gasket too much? to a point that the crush rings expand too much into the coolant and oil passages?

Not really, no; Not at this level of torque. I've gotten that answer from people much smarter than I. It is possible to compromise an old composite head gasket with too much pressure after a retorque, but whether that's what the cause of a BHG after a retorque or if the gasket was already blown prior is too difficult to say.